Field of the Invention
The present invention relates to mobile communication.
Related Art
3rd generation partnership project (3GPP) long term evolution (LTE) evolved from a universal mobile telecommunications system (UMTS) is introduced as the 3GPP release 8. The 3GPP LTE uses orthogonal frequency division multiple access (OFDMA) in a downlink, and uses single carrier-frequency division multiple access (SC-FDMA) in an uplink. The 3GPP LTE employs multiple input multiple output (MIMO) having up to four antennas. In recent years, there is an ongoing discussion on 3GPP LTE-advanced (LTE-A) evolved from the 3GPP LTE.
As disclosed in 3GPP TS 36.211 V10.4.0 (2011-12) “Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation (Release 10)”, 3GPP LTE/LTE-A may divide the physical channel into a downlink channel, i.e., a physical downlink shared channel (PDSCH) and a physical downlink control channel (PDCCH), and an uplink channel, i.e., a physical uplink shared channel (PUSCH) and a physical uplink control channel (PUCCH).
Meanwhile, in a next-generation system, a channel situation for a user equipment (UE) or a terminal like a small cell environment or a next-generation interference management (e.g., network-assisted interference cancellation (NAIC) technique may be considered, which is improved further than the existing environment.
In this case, introducing a high order modulation scheme such as 256 QAM may be considered as a part for improving spectral efficiency.
In terms of hardware implementation, for example, errors may occur in transmitting each modulated symbol at a transmitting end, such as non-linearity and phase distortion of a power amplifier and this is recognized as self interference to influence reducing a substantial signal-to-noise-plus-interference ratio (SINR) at a receiving end.
The influence of the self interference may express an error caused because the corresponding modulated symbol cannot be accurately expressed during transmission/reception in the form of an error vector magnitude (EVM).
Equation 1 given below is an example of the EVM.
                    EVM        =                                            P              error                                      P                              avg                ,                tx                                                                        [                  Equation          ⁢                                          ⁢          1                ]            
In the above description, Perror represents power for an error vector and Pavg,tx represents average transmit power of the transmitting end.
As a modulation order increases, an Euclidean distance between modulated symbols on a constellation may be reduced, therefore, there may be a problem in that performance deterioration in a system using a high order modulation scheme increases even with respect to the same EVM.